Water soluble elemental copper, such as copper sulfate, is known to possess algicidal qualities when used in circulating water systems. Unfortunately, copper ions easily precipitate in alkaline or near-alkaline water conditions as insoluble salts of oxides, hydroxides, and/or carbonates, removing the copper from the system and thus removing the ability of the copper ion to act as an algicide.
In order to improve the efficacy of copper as an algicide, sequestering agents, such as alkanolamines, aminocarboxylic acids or citric acid have been used to improve the stability of copper in these conditions. These simple, organic compounds contain amine, hydroxyl, and carboxyl functionalities that exhibit sequestration capacity for polyvalent cations. Problems remain however, because alkanolamines, aminocarboxylic acids, and citric acid deteriorate quickly in the presence of halogens and other oxidizers, bacteria, sunlight or heat, thus allowing the copper to become unsequestered and subject to loss due to precipitation.
Another problem encountered in water treatment applications, such as swimming pools, is that copper precipitates to form unsightly stains on the pool's surface. In particular, copper hydroxides, copper oxides and copper carbonates are known to cause unsightly stains that are difficult to remove.
A need therefore exists for a method of stabilizing soluble copper for longer periods of time during treatment and application, thereby increasing its effective life and preventing stains from occurring on swimming pool surfaces. The present invention addresses that need.